Fuel injection system



May 3, 6 5. 0. WOLFF FUEL INJECTION SYSTEM 2 Sheets-Sheet 1 Filed Dec.20, 1965 May 23, 1967 G. D. WOLFF FUEL INJECTION SYSTEM 2 Sheets-Sheet 2Filed Dec. 20, 1965 United States Patent 3,3203% FUEL FNJECTEUN SYSTEMGeorge D. Wolff, Hazel Crest, lill., assignor to Allis- ChalrnersManufacturing Company, Miiwaukee, Wis. Filed Dec. 20, 1965, Ser. No.522,007 8 Claims. (Cl, 1il3-2) This is a continuationin-part ofapplication Ser. No. 405,1-89, iiled Oct. 1964, now abandoned.

This invention relates to a fuel injection system for diesel engines andparticularly to precharging the fuel injection lines prior to injection.

In the usual fuel injection pump the delivery passage is connected tothe supply pressure chamber for a brief interval following injection toterminate injection. It is also known that pressure relief afterinjection is necessary in order to absorb the reflected pressure wavesfrom the nozzle. If such relief is not afforded, pressure surgesoccurring after cutoff of fuel delivery to the injector may causesecondary injection which in turn causes a decrease in combustionefliciency. Relieving the pressure by use of a retraction delivery valveor by connecting the fuel delivery lines briefly to the supply chamberor to a low pressure portion of the system is usually effective inpreventing secondary injection; however, voids often develop from thisrelief in the injection lines which cause erratic pump performance.Voids in the injection lines make it particularly difiicult to controlthe injection in the low speed range of the engine and at low fueldelivery.

In fuel injection pumps using retraction delivery valves, the retractionof the delivery valve serves to relieve pressure in the delivery line attermination of injection. More specifically the retraction deliveryvalve reduces the reflection of the pressure wave returning from theinjector after the end of the pumping stroke. To do this a small volumeof fuel, the retraction volume, is displaced by the delivery valve, uponits closing, from the high pressure system back into the pumpingchamber. Thus, a void is created into which the fuel carried in thereturning pressure wave from the injector is dumped. Ideally, the volumeof fuel carried in the returning wave is equal to the void created (theretraction volume) and in such a case the returning pressure wave iscompletely absorbed so that a reflection pressure wave will not becreated at the pump end of the delivery line.

The amplitude of the returning pressure wave and consequently the volumeof fuel carried by this wave, however, is not only a function ofdimensional parameters, such as delivery line ID and injector orificearea, but is also a function of the amplitude of the primary waveinitiated at the pump during the pumping stroke. It is known that theamplitude of the primary wave varies with speed and load. When theengine rpm. is increased the plunger moves faster and a pressure wavewith a higher amplitude is created. When the fuel delivery of the pumpis increased, the pressure buildup in the pump will be greater than witha smaller delivery. Thus, the amplitude of the primary pressure waveinitiated at the pump during the pumping stroke varies with engine speedand load and so also does the amplitude of the returning pressure wave.Ideally, therefore, a delivery valve retraction volume should also varywith speed and load. As this is not practical, a retraction volume isconventionally selected which is ideal only for one speed loadcombination. For all other conditions it will be a compromise i.e.either too large, resulting in a negative reflection of the returningwave and thus voids in the high pressure system, or too small, resultingin a positive reflection and thus possibly leading to secondaryinjections.

Thus, the development engineer is confronted with the problem oftailoring his injection equipment to achieve ice satisfactory injectionwith low injection quantities and low speeds (low idle) without havingsecondary injections with high injection quantities and high speeds(full load). The speed and load range of the modern diesel engine isprogressively expanding and the task of achieving satisfactory injectionthroughout this increasing range is becoming more and more diflicult.The beforementioned limitation of the conventional injection system isan important restrictive factor in the further development of highspeed, high BMEP diesel engines leading to such expensive solution asunit injectors or separate pumps for each cylinder.

Another serious problem has arisen as higher performance and greatereconomy of operation are sought in diesel engines. As the brake meaneffective pressure (BMEP) of diesel engines has increased, inwardlyopening fuel injectors, with high opening pressure, have become thegenerally accepted type of fuel injector. Inwardly opening injectorscharacteristically employ a differential area valve with high openingpressure and somewhat lower closing pressure. The spring loading of thevalve is chosen to provide a sufficiently high closing pressure toprevent combustion gases from entering the pressure chamber of theinjector.

As the cylinder pressures are increased, as by turbocharging, theinjectors have been designed with higher opening pressure so that theclosing pressure would be above the cylinder pressure. A high closingpressure results in high seating forces being imposed on the valve seat.These forces tend to pound out the seat, thus resulting in shortinjector life. Although engine output can be increased by increasingengine speed, there are well known practical limitations in this routeto increased performance. Increases in power, other than by increasingspeed, results in higher combustion pressures and higher injector valveseating forces and hence reduced valve seat life.

it is an object of this invention to provide a fuel injection systemwhich obviates the problems hereinbefore outlined.

It is a further object of this invention to provide an improved fuelinjection system for high BMEP diesel engines utilizing a distributortype fuel pump.

It is a further object of this invention to provide a new and improvedfuel injection system using a distributor type pump wherein theinjection lines are connected to a low pressure supply during a majorpart of the time that they are not used for injection and the injectorshave a relatively low opening pressure without the problem of combustiongases entering the pressure chamber of the injectors after injection.

It is a further object of this invention to provide a fuel pump whichachieves proper performance of the engine within a very wide speed andload range.

It is a further object of this invention to provide a fuel pump whereinvoids in the high pressure system are elimi nated prior to the beginningof the delivery stroke.

It is a further object of this invention to provide a fuel pump whereinthe fuel injection lines are connected to the fuel pump supply chamberto provide equalization of pressure in the injection lines andprecharging thereof during the time they are not being employed toinject fuel.

It is a further object of this invention to provide a fuel pump whichpermits a short period of fuel injection without the problems ofsecondary injection or voids in the fuel line.

It is a further object of this invention to provide a single plungerdistributor type fuel pump with a passageway in the plunger connectingthe delivery lines with the supply chamber during most of the periodbetween injections.

It is a further object of this invention to provide a fuel injectionsystem of the type having a low pressure zone, a high pressure zone andan intermediate pressure zone and to provide means for connecting thefuel delivery passageways to the intermediate pressure zone for themajor portion of time they are disconnected from delivery pressure.

These and other objects will be apparent to those familiar with the artwhen the following description is read in conjunction with the drawingsin which:

FIG. 1 is a view of a fuel injection system, including a fuel injectionpump in section, in which the present invention is incorporated;

FIG. 2 is a section view taken along the lines II-II in FIG. 1;

FIG. 3 is a section view taken along the line IIIIII in FIG. 2;

FIG. 4 is a partial view of the pump plunger; and

FIG. 5 is a section view taken along the line VV in FIG. 1.

Referring to FIG. 1, my precharged fuel injection system includes a pump8 having a plunger 11 reciprocated in a plunger bore 112 of the headportion of pump housing 9 by a cam 13 formed on the pump drive shaft 14.The plunger 11 is rotated by a gear train including gears 16, 17 ofsupply pump 15 and gears 1-8, 19. The plunger 11 is connected to rotatewith the gear 19 and reciprocate relative thereto. Gears 16 and 18 areintegrally formed to provide a gear cluster and gear 17 is nonrotatablysecured to the drive shaft 14.

The pump housing 9 includes a governor compartment 21, which is at fueltank pressure by virtue of its being connected thereto by a return lineindicated schematically by dot-dash lines 22. The housing 9 alsoincludes a supply chamber 26 which is supplied fuel by the gear pump 15by way of conduit 27 in which a fuel filter 23 is interposed. The supplypump 15 draws fuel from the fuel tank 29 by way of conduit 31. The fueltank 20 and governor compartment 21 may be maintained at nearatmospheric pressure and the supply chamber 26 is maintained at anintermediate pressure, such as 50 pounds per square inch, by a pressuremaintaining valve 32 disposed between the supply chamber 26 and thegovernor chamber 21. A plurality of fuel delivery passages 36 areadapted at their outer ends, by threaded openings 37, for connection tofuel injection conduits or lines leading to the injectors. The innerends of the passages 36 terminate, as illustrated in FIG. 2, at openings38 which are equally circumferentially spaced.

Although my precharged pump will operate satisfactorily with inwardlyopening (differential area) injectors,

I have found that outwardly opening injectors may be advantageouslyemployed. In FIG. 1, I show an out- .wardly opening injector 61connected in fluid communication to one of the passages 36 by line 62,indicated schematically.

As will be noted in FIGS. 1 and 3, the upper end of the bore 12 isclosed to form a high pressure chamber 41. The high pressure chamber 41is at injection pressures only during the upward movement (pumpingstroke) of the plunger 11. The plunger 11 includes a pumping portion 42,a distributing portion 43 and an effective stroke control portion 44.Referring also to FIGS. 2 and 3, the distributing portion 43 of theplunger, which serves as rotating valve means to cyclically andindividually connect in a sequential manner the high pressure chamber 41with the delivery passages 36, includes a radially opening port 46 whichis placed in free flow fluid communication with the injection pressurechamber 41 by an axial passage 47 in the plunger 11. The passage 47 isopen at its upper end and connects to radial passages 48 in theeffective stroke control portion 44- of the plunger 11, which cyclicallyregister with grooves 49 in control collar 51. FIG. 5 illustrates theregistrability of passages 48 with grooves 49.

As shown in FIGS. 1, 2, 3 and 4, a recess 55 is formed in thedistributing portion of the plunger 11 in circumferentially spacedrelation to port 46. The recess 55 has a circumferential width severaltimes the circumferential width of port 46 and is placed in free flowfluid communication with the supply chamber 26 by an axial groove 56. Asis illustrated in FIG. 2, the recess 55 places the fuel deliverypassages 36 in free flow fluid communication with the supply chamber 26during a substantial portion of the time that they are out of registrywith the port 46.

Operation of the fuel injection system As the plunger 11 commences itsupward stroke it simultaneously rotates so that its supply and spillpassages 48 move out of registery with the axial grooves 49. When thisoccurs further upward movement of the rotating plunger 11 effects highpressure in the injection chamber 41 and simultaneously brings thedelivery port 46 into registry with one of the delivery passages 36. Amajority of the other delivery passages 36 are connected to the supplychamber 26 by way of recess 55 and groove 56. As the plunger continuesto rotate and move upwardly in its pumping stroke, the top series ofpassages 48 in the control portion of the plunger will move above thecollar 51, thereby spilling the pressure fluid from the pressurizeddelivery passage 36 by way of the delivery port 46 which still is inregistration therewith. Further rotative movement of the plunger willmove the port 4.6 out of registry with the pressure relieved passage 36and connect the latter in free flow fluid communication with thepassageway formed by recess 55 and groove 56.

When the upper row of supply passages 48 moves above the collar andrelieves the pressure in the delivery passage 36 with which the deliveryport 46 registers at the time, the injector valve at the engine cylinderwill close and the returning pressure wave in the passage 36 ischanneled to the supply chamber 26 by way of delivery port 46, passages47, 48 and grooves 49. Thus the returning pressure wave from theinjector travels to the supply chamber, where it is absorbed, by way ofport 46, passages 47, 48. The time interval for this communicationbetween passage 36 and chamber 26 is not SllfilClfiIlt to permitequalization of pressure in the delivery passage and in fact a lowpressure condition in the delivery passage may result which in turn mayinduce formation of cavities. The cavities of which I speak are thoseformed of vapor, entrained in air and dissolved air which is liberatedfrom the liquid fuel at low pressure. The use of passage means 55, 56,which serve as a rotating valve to cyclically connect the deliverypassages 36 to the supply chamber 26, is effective to equalize thepressure in, and precharge the delivery passages 36, since the latterare connected to the supply chamber 26 for a relatively long timeinterval.

As is apparent from my construction, during pump operation theindividual delivery passages 36 are connected to the supply chamber 26for a major portion of the time, that is, over one-half the time. In apump having three or more delivery passages, it may be practical to useas short a time interval for precharging as the time interval requiredfor two injection cycles. Equalization of the pressure in the deliverypassages and precharging them to supply chamber pressure, insures equaldelivery of pressure fluid to the cylinder injectors during injection.

Although a fuel pump using my precharging concept could be provided witha delivery valve between the injection chamber 41 and the port 46, Ihave found the delivery valve to be unnecesary and its eliminationresults in further improvement in engine performance. The delivery valveis a source of reflection for the returning pressure wave in thedelivery lines and hence its elimination is beneficial. Also,elimination of the delivery valve decreases the volume of the highpressure system of the pump with resulting improvement in deliveryperformance. My fuel pump also makes it possible for a given fuel systemto have a shorter duration of injection and this provides fast burningof the fuel and more efficient combustion.

Having essentially elimiated the reflected pressure wave by means of theprecharging concept, I have found that diesel injectors with outwardlyopening valves may be used to great advantage over inwardly openinginjectors. As herein before discussed the closing pressure for inwardlyopening injectors has necessarily been increased as engine BMEP hasincreased, thus reducing valve seat life. Since the combustion gasestend to force the outwardly opening valve 63 closed rather than open (asoccurs in an inwardly opening injector), a lower closing pressure can beused for valve 63 without permitting entrance of combustion gases intoinjector pressure chamber 64. Reducing closing pressure of the injectorvalve results in longer life of the valve seat 66. Also, as is wellknown, the cost of outwardly opening injectors is substantially lessthan inwardly opening nozzles.

My prechar-ged fuel injection system provides improved fuel injectionthrough precise and equal delivery of fuel to the engine cylinders,permits higher cylinder operating pressures without attendant problemsof combustion gases entering the injectors or excessive injector valveclosing pressures and affords a marked reduction in cost of injectionequipment through reduced pump and injector costs.

The embodiments of the invention for which an exelusive property orprivilege is claimed are defined as follows:

1. In a distributor type fuel injection pump the combination comprising:

a pump housing including a bore, a plurality of valveless deliverypassages adapted to connection to fuel delivery lines, respectively, aninjection pressure chamber, and a supply chamber, means supplying fuelto said supply chamber and maintaining the latter at a pressuresubstantially above atmospheric pressure, means for cyclicallytransferring fuel from said supply chamber to said injection pressurechamber and for pressurizing it to an injection pressure including areciprocable pump plunger in said bore, and

rotating valve means in said housing between said in jection pressurechamber and said delivery passages cyclically and individuallyconnecting said delivery passages to said injection pressure chamberduring the pumping stroke of said plunger and passage means in saidvalve means independent of said second named means cyclically connectingsaid delivery passages in continuous free flow fluid communication withsaid supply chamber during a major portion of the time they aredisconnected from said injection pressure chamber.

2. The fuel pump set forth in claim 1 wherein said delivery passagesnumber at least three and during an injection cycle and deliverypassages are in free flow fluid communication with said supply chamberfor a greater interval of time than the interval of time required toeffect injection through two of said delivery passages.

3. In a distributor type fuel injection pump the combination comprising:

a pumping housing including a high pressure chamber, a supply chamber, abore between said chambers, and a plurality of delivery passagesterminating at their inner ends at said bore in circumferentially spacedopenings and adapted at their outer ends for connection to fuel deliverylines, means suplying fuel to said supply chamber and maintaining thelatter at a pressure substantially above atmospheric pressure, and

a pump plunger reciprocably and rotatably mounted in said bore havingcyclically open and closed passage means extending between said highpressure chamber and said supply chamber, and

a valve portion defining a passage means operable upon rotation of saidplunger to cyclically and individually connect said delivery passages tosaid high pressure chamber during injection and another passage meansindependent of said cyclically open and closed pasage means operableupon rotation of said plunger to cyclically connect said deliverypassages in free flow fluid communication with said supply chamberduring a substantial portion of the time the delivery passages aredisconnected from said high pressure chamber.

4. The structure set forth in claim 3 wherein said another passage meansis a recess registrable with said openings during rotation of saidplunger and an axially extending groove in the periphery of said plungerextending between said recess and a portion of said plunger disposed insaid supply chamber.

5. A fuel injection pump comprising:

a housing including a supply chamber,

a plunger bore opening at one end into said supply chamber and closed atits other end to provide a high pressure chamber,

fuel delivery openings intermediate said high pressure chamber and saidsupply chamber, equally spaced circumferentially about and opening intosaid bore,

fuel delivery passages connected to said openings,

respectively,

a plunger reciprocably and rotatively disposed in said bore including adistributing portion,

a radially opening port in said distributing portion,

passage means in said plunger between said high pressure chamber andsaid port,

a circumferentially extending recess in said distributing portion spacedcircumferentially from said port and in constant free flow communicationwith said supply chamber, said recess extending circumferentially adistance greater than the circumferential distance between said fueldelivery openings,

drive means for reciprocating said plunger in said bore to pump fuel andfor rotating said plunger to distribute fuel being pumped thereby tosaid openings by cyclically registering said port with said openings oneat a time.

6. A fuel injection pump comprising:

a housing including a supply chamber a plunger bore opening at one endinto said supply chamber and closed at its other end to provide a highpressure chamber, and

a plurality of valveless fuel delivery passages having inner endsterminating in equally and circumferentially spaced openingsrespectively at said bore intermediate said high pressure chamber andsaid supply chamber and having outer ends adapted for connection withfuel injection conduits respectively.

a plunger reciprocably and rotatively disposed in said bore including adistributing portion,

a radially opening port in said distributing portion in communicationwith said high pressure chamber,

drive means for reciprocating said plunger in said bore to pump fuel andfor rotating said plunger to sequentially distribute fuel to saiddelivery passages by cyclically registering said port with said fueldelivery passages, and a passageway formed in said distributing portionplacing said delivery passages in continuous free flow fluidcommunication with said supply chamber during a portion of thetime theyare out of registry with said port, said portion of time being at leastas great as the time interval for injections through two adjacentdelivery passages. 7. A fuel injection system comprising: an injectionpump having a housing including a high pressure chamber,

a supply chamber,

a bore extending between said chambers, and

at least three valveless delivery passages defining openings in saidbore between said chambers and at equally spaced circumferentialintervals,

a rotatable and reciprocable pump plunger in said bore having a radiallyopening port cyclically registrable with said passages one at a timeduring rotating of said plunger,

passage means connecting said port in fluid receiving relation to saidhigh pressure chamber, cyclically open and closed passage meansextending between said high pressure chamber and said supply chamber,eans maintaining said supply chamber at an intermediate pressure, and

passage means independent of said cyclically open and closed passagemeans continuously connecting said delivery passages to said supplychamher during a substantial portion of the time they are out ofregistry with said port, said portion of time being at least twice thetime required for said port to rotate through two of saidcircumferential intervals.

8. A fuel injection pump comprising: wall means defining a high pressurechamber,

8 a supply chamber,

a bore, and a plurality of valveless delivery passages adapted at theirouter ends for connection to fuel injection conduits respectively andterminating at their inner ends in said bore at equally andcircumferentially spaced openings, means maintaining said supply chamberat an intermediate pressure means for cyclically transferring fuel fromsaid supply chamber to said high pressure chamber and for cyclicallypressurizing the transferred fuel to an injection pressure including areciprocable pump plunger, rotating valve means in said bore cyclicallyand individually connecting said delivery passages to said high pressurechamber to effect delivery of fuel therethrough at injection pressure,and passage means independent of said second named means connecting saiddelivery passages in continuous free flow fluid communication with saidsupply chamber during at least one quarter of the time the deliverypassages are disconnected from said high pressure chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,544,561 3/1951Meyer 103-2 2,804,825 9/1957 Mansfield et al 103-41 2,813,523 11/1957Bischofl' 103-2 2,965,087 12/1960 Bischolf et al 103-2 2,969,784 1/1961High 103-2 3,023,705 3/1962 Heiser 103-2 3,099,217 7/1963 Bessiere 103-23,146,716 9/1964 Dreisin 103-2 FOREIGN PATENTS 359,603 10/1931 GreatBritain.

804,026 11/1958 Great Britain.

971,536 9/1964 Great Britain.

349,124 11/1960 Switzerland.

DONLEY I. STOCKING, Primary Examiner.

W. J. KRAUSS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,320,892 May 23, 1967 George D. Wolff It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 5 line 35, "to" should read for line 58 "and" should read saidline 72, "suplying" should read supplying Signed and sealed this 19thday of August 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. E.

Attesting Officer Commissioner of Patents

1. IN A DISTRIBUTOR TYPE FUEL INJECTION PUMP THE COMBINATION COMPRISING: A PUMP HOUSING INCLUDING A BORE, A PLURALITY OF VALVELESS DELIVERY PASSAGES ADAPTED TO CONNECTION TO FUEL DELIVERY LINES, RESPECTIVELY, AN INJECTION PRESSURE CHAMBER, AND A SUPPLY CHAMBER, MEANS SUPPLYING FUEL TO SAID SUPPLY CHAMBER AND MAINTAINING THE LATTER AT A PRESSURE SUBSTANTIALLY ABOVE ATMOSPHERIC PRESSURE, MEANS FOR CYCLICALLY TRANSFERRING FUEL FROM SAID SUPPLY CHAMBER TO SAID INJECTION PRESSURE CHAMBER AND FOR PRESSURIZING IT TO AN INJECTION PRESSURE INCLUDING A RECIPROCABLE PUMP PLUNGER IN SAID BORE, AND ROTATING VALVE MEANS IN SAID HOUSING BETWEEN SAID INJECTION PRESSURE CHAMBER AND SAID DELIVERY PASSAGES CYCLICALLY AND INDIVIDUALLY CONNECTING SAID DELIVERY PASSAGES TO SAID INJECTION PRESSURE CHAMBER DURING THE PUMPING STROKE OF SAID PLUNGER AND PASSAGE MEANS IN SAID VALVE MEANS INDEPENDENT OF SAID SECOND NAMED MEANS CYCLICALLY CONNECTING SAID DELIVERY PASSAGES IN CONTINUOUS FREE FLOW FLUID COMMUNICATION WITH SAID SUPPLY CHAMBER DURING A MAJOR PORTION OF THE TIME THEY ARE DISCONNECTED FROM SAID INJECTION PRESSURE CHAMBER. 